Fluid control device and pump

ABSTRACT

A pump ( 1 ) includes a vibrating plate ( 15 ) that has a central part ( 21 ), a frame part ( 22 ), and connecting parts ( 23  to  26 ), a piezoelectric element ( 16 ) that is stacked over the central part ( 21 ) and configured to cause flexural vibrations to occur concentrically from the central part ( 21 ) to the connecting parts ( 23  to  26 ), and an opposed plate ( 13 ) that is stacked over the frame part ( 22 ) and positioned facing each of the connecting parts ( 23  to  26 ) with a spacing therebetween. The vibrating plate ( 15 ) has such a resonant mode that an antinode occurs in each of the central part ( 21 ) and the connecting parts ( 23  to  26 ). The opposed plate ( 13 ) has, at positions facing the connecting parts ( 23  to  26 ), a plurality of channel holes ( 39  to  43 ) through which a fluid flows.

This is a continuation of International Application No.PCT/JP2015/054531 filed on Feb. 19, 2015 which claims priority fromJapanese Patent Application No. 2014-180355 filed on Sep. 4, 2014 andJapanese Patent Application No. 2014-031372 filed Feb. 21, 2014. Thecontents of these applications are incorporated herein by reference intheir entireties.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

The present disclosure relates to a fluid control device that controlsthe flow of fluid by using a driver in which vibration is produced, anda pump that includes the fluid control device and sucks and dischargesfluid.

Description of the Related Art

Pumps that utilize vibration of a piezoelectric element are commonlyused (see, for example, Patent Documents 1 and 2). Such pumps are usedfor purposes such as directing outside air on a component that has risenin temperature to cool the component, and conveying fluid such as oxygenin a fuel cell.

FIG. 16 schematically illustrates major components of a conventionalpump. A conventional pump 101 illustrated in FIG. 16 includes a housing102, a vibrating plate 103, an opposed plate 104, and a piezoelectricelement 105. The vibrating plate 103, the opposed plate 104, and thepiezoelectric element 105 are accommodated in the housing 102. Theopposed plate 104 defines a pump chamber 110 inside the housing 102. Thevibrating plate 103, which is provided inside the pump chamber 110, ispositioned facing the opposed plate 104 with a spacing therebetween. Theouter peripheral portion of the vibrating plate 103 is elasticallysupported by the housing 102. The piezoelectric element 105 is stuck onthe vibrating plate 103, forming an actuator 111 together with thevibrating plate 103. The housing 102 has, on its upper face, a channelhole 112 that provides communication between the inside and outside ofthe pump chamber 110. The opposed plate 104 is provided with a channelhole 113 that communicates with the inside of the pump chamber 110. Thehousing 102 has, on its lower face, channel holes 114 that communicatewith the pump chamber 110 through the channel hole 113 and also with theoutside.

When voltage is applied to the piezoelectric element 105 of the pump101, the vibrating plate 103 undergoes flexural vibration in thethickness direction as the piezoelectric element 105 attempts to expandor contract in the in-plane direction. This creates pressurefluctuations in the fluid layer that is sandwiched between the vibratingplate 103 and the opposed plate 104 inside the pump chamber 110,producing a fluid flow such that the fluid is sucked into the pumpchamber 110 through the channel holes 114 and 113 and the fluid isdischarged to the channel hole 112 from the pump chamber 110.

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2013-068215

Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 2013-053611

BRIEF SUMMARY OF THE DISCLOSURE

There are demands for reduced physical size and improved drivingefficiency of this type of pump. Unfortunately, a reduction in thephysical size of the pump tends to lead to a decrease in drivingefficiency. Thus, with conventional structures, it is difficult toachieve both reduced physical size and improved driving efficiency atthe same time.

Accordingly, it is an object of the present disclosure to provide afluid control device and a pump having improved driving efficiency overconventional designs without an increase in physical size, or reducedphysical size over conventional designs without a decrease in drivingefficiency.

A fluid control device according to the present disclosure includes avibrating plate that has a central part, a frame part surrounding thecentral part, and a connecting part connecting between the central partand the frame part, a driver stacked over the central part, the driverbeing configured to vibrate the vibrating plate in a flexural mannerfrom the central part to the connecting part, and an opposed platestacked over the frame part, the opposed plate being positioned facingat least the connecting part with a spacing between the opposed plateand the connecting part. The vibrating plate has a resonant mode suchthat an antinode occurs in each of the central part and the connectingpart. The opposed plate has a plurality of channel holes though which afluid flows, the channel holes being each located at a position facingthe connecting part.

According to this configuration, channel holes are each positionedfacing the connecting part where an antinode is formed. As a result, thetotal amount of parallel fluid flows through the channel holes can beincreased. This allows for an improvement in driving efficiency, thusenabling a reduction in physical size while achieving a desired flowrate or pressure.

The connecting part may include, at a position facing each of thechannel holes, a striking part that is locally increased in width asviewed from the channel hole. This configuration allows the amplitude ofvibration of the striking part to be increased, without decreasing thearea over which the vibrating plate (striking part) and the fluid arepositioned facing each other in the vicinity of the channel holes thatdirectly contribute to fluid control. This makes it possible to reduceunwanted load on the vibrating plate and the driver, thus improvingdriving efficiency.

The connecting part may include a projection that is provided at aposition facing each of the channel holes and projects toward thechannel hole. Alternatively, the opposed plate may include, around eachof the channel holes, a projection that projects toward the vibratingplate. As a result of these configurations, in comparison to the spacingprovided between the vibrating plate and the opposed plate in thevicinity of the channel holes that directly contribute to fluid control,the spacing between the vibrating plate and the opposed plate in otherareas can be increased. This makes it possible to reduce unwanted loadon the vibrating plate and the driver to further improve drivingefficiency.

The opposed plate may include a movable part capable of flexion providedaround each of the channel holes, and a restraining part that restrainsan area around the movable part. For example, the movable part can beprovided by forming the opposed plate with reduced thickness in themovable part and with increased thickness in the restraining part.Alternatively, for example, the movable part can be formed by providingthe channel plate, which is stacked over the side of the opposed plateopposite to the vibrating plate, with an opening that is positionedfacing each of the channel holes of the opposed plate and the areaaround the channel hole. With this configuration, vibration of theconnecting part also causes the movable part positioned facing theconnecting part to vibrate in response to this vibration. The vibrationof the movable part and the vibration of the connecting part thencouple, allowing fluid to flow through each channel hole in a fixeddirection even without the presence of a structure that regulates thedirection of fluid flow, such as a check valve. This facilitates fluidflow while eliminating the need for a component such as a check valve,thus allowing for improved driving efficiency.

Preferably, the movable part has such a shape in plan view that has amajor axis extending in a direction in which antinodes are produceduniformly in the connecting part, and a minor axis extending in adirection orthogonal to the major axis, for example, an elliptical shapeor an oval shape. This configuration allows the movable part to beincreased in dimension in the major axis direction while preventing adecrease in the natural frequency of the movable part. As a result, theamplitude of vibration occurring near each end portion along the majoraxis of the movable part can be increased in comparison to when themovable part has the shape of a perfect circle. When vibration causesboth principal faces of the connecting part positioned facing themovable part to undergo expansion or contraction in the minor axisdirection, an opposite contraction or expansion is produced in the majoraxis direction. This creates such a vibration in the connecting partthat causes the connecting part to flex as viewed in the minor axisdirection. This vibration has maximum amplitude at each end along themajor axis of the connecting part. Consequently, if vibration producedin the movable part positioned facing the connecting part has a smallamplitude at each end portion along the major axis of the movable part,a collision with the connecting part can occur. Accordingly, theamplitude of vibration produced at each end portion along the major axisof the movable part is increased as described above, thus reducing therisk of a collision with the connecting part positioned facing themovable part. This makes it possible to, for example, prevent occurrenceof abnormal vibration or noise, or prevent a decrease in pressure causedby such a collision.

The channel of the channel part includes an opening that is positionedfacing each of the channel holes of the opposed plate and an area aroundthe channel hole, an extension that is extended laterally from theopening, and a channel hole that is open to an external space andcommunicates with the opening through the extension. This configurationallows each channel hole of the opposed plate and the channel hole ofthe cover plate to be positioned away from each other in plan view, thusreducing leakage of vibrating sound generated by vibration of thevibrating plate.

Preferably, the components stacked over the frame part of the vibratingplate each have a coefficient of linear expansion substantially equal tothe coefficient of linear expansion of the vibrating plate. This makesit possible to further reduce deformation resulting from a difference incoefficient of linear expansion.

The opposed plate may be stacked over the vibrating plate by using anadhesive containing electrically conductive particles. Preferably, inthis case, the electrically conductive particles have a diameterequivalent to the spacing between the opposed plate and the vibratingplate. This configuration ensures a uniform, desired spacing between theopposed plate and the vibrating plate even when the opposed plate andthe vibrating plate are bonded together with an adhesive. This makes itpossible to reduce variations in the performance of the fluid controldevice.

Preferably, the vibrating plate and the opposed plate are each made ofan electrically conductive material, the opposed plate is stacked overthe vibrating plate by using an adhesive containing electricallyconductive particles, and the electrically conductive particles have adiameter equivalent to the spacing between the opposed plate and thevibrating plate. This configuration ensures a uniform, desired spacingbetween the opposed plate and the vibrating plate even when the opposedplate and the vibrating plate are bonded together with an adhesive. Thismakes it possible to reduce variations in the performance of the fluidcontrol device. Further, power can be fed to the driver through theopposed plate.

The fluid control device may include an insulating layer stacked overthe frame part, the insulating layer being positioned over a side of thevibrating plate over which the driver is stacked, and a power feedingplate stacked over the vibrating plate with the insulating layerinterposed between the power feeding plate and the vibrating plate, thepower feeding plate having an internal connection terminal formed in apart of the power feeding plate, the internal connection terminal beingconnected to the driver. With this configuration, the presence of theinsulating layer prevents the power feeding plate and the vibratingplate from being brought into electrical continuity with each other,thus allowing power to be fed to the driver through the power feedingplate.

In this case, the insulating layer may include an adhesive mixed withnon-electrically conductive particles. With this configuration, thenon-electrically conductive particles reliably prevent electricalcontinuity between the power feeding plate and the vibrating plate.

The insulating layer may include an insulating coating provided betweenthe vibrating plate and the power feeding plate. With thisconfiguration, the insulating coating reliably prevents electricalcontinuity between the power feeding plate and the vibrating plate. Thepresence of the insulating coating eliminates the need for the adhesiveto contain non-electrically conductive particles, thus allowing for easyconstruction of the insulating layer.

The fluid control device may further include a metal plate stacked overthe frame part of the vibrating plate. With this configuration, evenwhen the insulating layer stacked between the vibrating plate and thepower feeding plate is made of a soft material with a low density and alow Young's modulus, such as resin, the presence of the metal platebetween the vibrating plate and the insulating layer allows theconnecting part of the vibrating plate to be reliably secured in place,thus preventing vibration from leaking to other components through theframe part. This prevents driving efficiency or other performancefeatures of the fluid control device from decreasing. The insulatinglayer may be formed by a coating of insulating film applied on thesurface of the metal plate. In this case as well, stacking the vibratingplate and the insulating layer with the metal plate interposedtherebetween allows the connecting part of the vibrating plate to bereliably secured in place.

The frame part of the vibrating plate may have a groove located on aside of the vibrating plate over which the driver is stacked, and theinsulating layer and the power feeding plate may be disposed in thegroove. This configuration allows the thickness of the device to bereduced.

Preferably, the opposed plate may have a channel hole also at a positionfacing the central part. This configuration allows the number of channelholes to be further increased, thus enabling a further improvement infeatures such as flow rate and driving efficiency.

Preferably, the fluid control device further includes a stacking platefurther stacked over the vibrating plate and the driver, the vibratingplate, the driver, and the stacking plate form three layers including anupper layer, a middle layer, and a lower layer, and the magnituderelationship of the coefficient of linear expansion of the middle layerwith respect to the coefficient of linear expansion of the upper layeris identical to the magnitude relationship of the coefficient of linearexpansion of the middle layer with respect to the coefficient of linearexpansion of the lower layer. This configuration makes it possible toreduce deformation in components such as the vibrating plate and thedriver resulting from the difference in coefficient of linear expansionbetween the vibrating plate and the driver.

Preferably, among the three layers including the vibrating plate, thedriver, and the stacking plate, a component corresponding to a layer incontact with the driver has a coefficient of linear expansion greaterthan the coefficient of linear expansion of the driver. Thisconfiguration causes compressive stress to be exerted on the driver,thus reducing breakage of the driver. If the driver is present in themiddle layer, compressive stress can be uniformly exerted on the driver,thus reducing breakage of the driver compared to cases such as when atwo-layer construction is employed or when the driver is disposed in theupper layer or lower layer.

Preferably, the opposed plate includes a first opposed plate and asecond opposed plate, the first opposed plate being disposed facing oneprincipal face of the vibrating plate, the second opposed plate beingdisposed facing the other principal face of the vibrating plate. Thisconfiguration allows a greater number of channel holes to be provided inthe opposed plate, thus enabling a further improvement in features suchas flow rate and driving efficiency.

Desirably, the driver includes a first driver and a second driver, thefirst driver being disposed facing one principal face of the vibratingplate, the second driver being disposed facing the other principal faceof the vibrating plate. This configuration makes it possible to reducedeformation in the stack of the vibrating plate and the driver resultingfrom the difference in coefficient of linear expansion between thevibrating plate and the driver, while increasing the amplitude ofvibration of the vibrating plate. This enables a further improvement infeatures such as flow rate and driving efficiency.

Preferably, the pump according to the present disclosure includes theabove-mentioned fluid control device, has a pump chamber thataccommodates the vibrating plate and the driver, and the opposed plateforms a part of the inner wall of the pump chamber.

According to the present disclosure, channel holes are each positionedfacing the connecting part of the vibrating plate, allowing for anincrease in the amount of fluid entering or exiting through the channelholes. This enables an improvement in driving efficiency without anincrease in physical size, or enables a reduction in physical sizewithout a decrease in driving efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an external perspective view of a pump according to a firstembodiment of the present disclosure.

FIG. 2 is an exploded perspective view of the pump according to thefirst embodiment of the present disclosure.

Each of FIG. 3A-3C illustrates a vibrating plate and a piezoelectricelement according to the first embodiment of the present disclosure.

FIG. 4 is a cross-sectional view of the pump according to the firstembodiment of the present disclosure.

Each of FIGS. 5A and 5B schematically illustrates the operation of afluid control part according to the first embodiment of the presentdisclosure.

FIG. 6 is an exploded perspective view of a pump according to a secondembodiment of the present disclosure.

Each of FIG. 7A-7D is a plan view of a vibrating plate, an opposedplate, a channel plate, and a cover plate according to the secondembodiment of the present disclosure.

Each of FIGS. 8A and 8B schematically illustrates how the vibratingplate and the opposed plate vibrate according to the second embodimentof the present disclosure.

FIG. 9 is an exploded perspective view of a pump according to a thirdembodiment of the present disclosure.

FIG. 10 is an exploded perspective view of a pump according to a fourthembodiment of the present disclosure.

FIG. 11 is an exploded perspective view of a pump according to a fifthembodiment of the present disclosure.

Each of FIGS. 12A-12C illustrates a pump according to sixth, seventh andeighth embodiments of the present disclosure.

FIGS. 13A-13C illustrate a pump according to ninth, tenth and eleventhembodiments of the present disclosure.

FIG. 14 is an exploded perspective view of a pump according to a twelfthembodiment of the present disclosure.

FIGS. 15A and 15B are an enlarged perspective view of the pump accordingto the twelfth embodiment of the present disclosure.

FIG. 16 illustrates major components of a conventional pump.

DETAILED DESCRIPTION OF THE DISCLOSURE First Embodiment

Hereinafter, a pump 1 according to a first embodiment of the presentdisclosure will be described with reference to an air pump that sucksgas as an example.

FIG. 1 is an external perspective view of the pump 1. As illustrated inFIG. 1, the pump 1 includes a housing 2, and external connectionterminals 3 and 4. The external connection terminals 3 and 4 are eachconnected to an external power source, and applied with analternating-current drive signal. The housing 2, which has a principalface (upper principal face) 5 and a principal face (lower principalface) 6, is a hexahedron with a small thickness between the principalfaces 5 and 6. The housing 2 also has a channel hole 50 provided at theupper principal face 5, and channel holes 31, 32, 33, and 34 (see FIG.2) provided at the lower principal face 6.

FIG. 2 is an exploded perspective view of the pump 1. As illustrated inFIG. 2, the pump 1 includes the following components stacked in theorder stated below: a cover plate 11, a channel plate 12, an opposedplate 13, an adhesion layer 14 (see FIG. 4), a vibrating plate 15, apiezoelectric element 16, an insulating plate 17, a power feeding plate18, a spacer plate 19, and a lid plate 20.

The cover plate 11, which is exposed at the lower principal face 6 ofthe housing 2, is stuck on the lower face of the channel plate 12 byusing adhesive (not illustrated) or other materials. The cover plate 11has the channel holes 31, 32, 33, and 34 provided at the lower principalface 6 of the housing 2. The channel holes 31, 32, 33, and 34 have acircular shape. In the first embodiment, the channel holes 31, 32, 33,and 34 are inlets for sucking gas from the external space.

The channel plate 12 is stacked between the cover plate 11 and theopposed plate 13. The channel plate 12 is stuck on the upper face of thecover plate 11 and the lower face of the opposed plate 13 by usingadhesive (not illustrated) or other materials. The channel plate 12 hasopenings 35, 36, 37, and 38 provided at its upper and lower faces. Theopenings 35, 36, 37, and 38 have a circular shape with a diameter largerthan the diameter of the channel holes 31, 32, 33, and 34 of the coverplate 11. The openings 35, 36, 37, and 38 respectively communicate withthe channel holes 31, 32, 33, and 34 of the cover plate 11.

The opposed plate 13 is stacked between the channel plate 12 and thevibrating plate 15. The opposed plate 13 is stuck on the upper face ofthe channel plate 12 by using adhesive (not illustrated) or othermaterials, and is stuck on the lower face of the vibrating plate 15 byusing the adhesion layer 14 (see FIG. 4). The opposed plate 13 is madeof metal, and includes the external connection terminal 3 that projectsoutward. The opposed plate 13 also has channel holes 39, 40, 41, and 42at its upper and lower faces. The channel holes 39, 40, 41, and 42 havea circular shape with a diameter smaller that the diameter of theopenings 35, 36, 37, and 38 of the channel plate 12. The channel holes39, 40, 41, and 42 respectively communicate with the openings 35, 36,37, and 38 of the channel plate 12, and also communicate with a pumpchamber 51 (see FIG. 4) described later.

The adhesion layer 14 (see FIG. 4), which is stacked between the opposedplate 13 and the vibrating plate 15, is bonded to the upper face of theopposed plate 13 and the lower face of the vibrating plate 15. Theadhesion layer 14 is formed in a frame-like shape so as to be overlappedwith a frame part 22 of the vibrating plate 15. The space inside theframe-like shape of the adhesion layer 14 constitutes a part of the pumpchamber 51 (see FIG. 4). The adhesion layer 14 includes a plurality ofelectrically conductive particles contained in a thermosetting resinsuch as an epoxy resin. The electrically conductive particles are madeof, for example, silica or resin coated with an electrically conductivemetal. Since the adhesion layer 14 contains a plurality of electricallyconductive particles as mentioned above, the thickness of the adhesionlayer 14 around its entire circumference can be made substantially equalto the particle diameter of the electrically conductive particles andthus uniform. Accordingly, the presence of the adhesion layer 14 allowsthe opposed plate 13 and the vibrating plate 15 to be positioned facingeach other with a uniform spacing between the opposed plate 13 and thevibrating plate 15. Further, the opposed plate 13 and the vibratingplate 15 can be made electrically continuous by using the electricallyconductive particles present in the adhesion layer 14.

The vibrating plate 15, which is made of a metal, for example, SUS430,is stacked between the opposed plate 13 and the insulating plate 17. Thevibrating plate 15 includes a central part 21, the frame part 22, andconnecting parts 23, 24, 25, and 26. The central part 21 has a circularshape in plan view. The frame part 22, which has a rectangularframe-like shape with an opening in plan view, surrounds the peripheryof the vibrating plate 15. Each of the connecting parts 23, 24, 25, and26 is in the form of a beam connecting between the central part 21 andthe frame part 22. The frame part 22 is stuck on the upper face of theopposed plate 13 by using the adhesion layer 14 (see FIG. 4), and stuckon the lower face of the insulating plate 17 by using adhesive (notillustrated) or other materials. The vibrating plate 15 has openings 43,44, 45, and 46 surrounded by the central part 21, the frame part 22, andthe connecting parts 23, 24, 25, and 26. The openings 43, 44, 45, and 46constitute a part of the pump chamber 51 (see FIG. 4).

The vibrating plate 15 may be made of a material other than SUS430, forexample, an iron alloy such as SUS301, SUS304, or SUS631, a copper alloysuch as phosphor bronze, beryllium bronze, or a copper-titanium alloy,an aluminum alloy, a nickel alloy, carbon, an amorphous metal, or resin.

The piezoelectric element 16, which has an electrode provided on each ofthe upper and lower faces of a sheet made of a piezoelectric material,corresponds to the “driver” according to the present disclosure. Thepiezoelectric element 16 exhibits piezoelectricity such that thepiezoelectric element 16 increases or decreases in area when subjectedto an electric field applied in the thickness direction. Using thepiezoelectric element 16 as a driver allows the thickness of the driverto be reduced, enabling miniaturization of a fluid control part 59 andthe pump 1 described later. The piezoelectric element 16, which isdisc-shaped, is stuck on the upper face of the central part 21 of thevibrating plate 15 by using adhesive (not illustrated) or othermaterials. The electrode on the lower face of the piezoelectric element16 is electrically connected to the external connection terminal 3, viathe vibrating plate 15, the adhesion layer 14, and the opposed plate 13.The electrode on the lower face of the piezoelectric element 16 may notbe provided but may be substituted for by use of the vibrating plate 15that is made of metal.

The piezoelectric element 16 is made of a piezoelectric material with acoefficient of linear expansion lower than that of the vibrating plate15. The piezoelectric element 16 is bonded to the central part 21 byusing a thermosetting adhesive. Thus, when thermosetting adhesive isheated and allowed to set, a compressive stress is allowed to remain inthe piezoelectric element 16 under normal temperature environments. Thismakes the piezoelectric element 16 resistant to breakage. Suitableexamples of the piezoelectric material of the piezoelectric element 16include lead zirconate titanate (PZT)-based ceramics. PZT-based ceramicshave a coefficient of linear expansion of substantially zero, which issufficiently lower than that of the metallic material constituting thevibrating plate 15, such as SUS430 (which has a coefficient of linearexpansion of approximately 10.4×10⁻⁶K⁻¹).

The insulating plate 17, which is stacked between the vibrating plate 15and the power feeding plate 18, is stuck on the upper face of the framepart 22 of the vibrating plate 15 and the lower face of the powerfeeding plate 18 by using adhesive (not illustrated) or other materials.The insulating plate 17 corresponds to the insulating layer according tothe present disclosure. Other than using the insulating plate 17, theinsulating layer may be formed by a method such as coating the surfaceof the vibrating plate 15 or the power feeding plate 18 with aninsulating material, forming an oxide film on the surface of thevibrating plate 15 or the power feeding plate 18, or applying a coatingof a mixture of an adhesive having insulating property andnon-electrically conductive particles. Alternatively, a plurality of theabove-mentioned components having insulating property may be combined toform the insulating layer. The insulating plate 17 has a rectangularframe-like shape with an opening 47 in plan view. The opening 47constitutes a part of the pump chamber 51 (see FIG. 4). The insulatingplate 17, which is made of insulating resin, provides electricalinsulation between the power feeding plate 18 and the vibrating plate15. The thickness of the insulating plate 17 is the same as or slightlylarger than the thickness of the piezoelectric element 16.

The power feeding plate 18, which is stacked between the insulatingplate 17 and the spacer plate 19, is stuck on the upper face of theinsulating plate 17 and the lower face of the spacer plate 19 by usingadhesive (not illustrated) or other materials. The power feeding plate18 has a substantially rectangular frame-like shape with an opening 48in plan view. The opening 48 constitutes a part of the pump chamber 51(see FIG. 4). The power feeding plate 18, which is made of metal,includes an internal connection terminal 27 that projects into theopening 48, and the external connection terminal 4 that projectsoutward. The distal end of the internal connection terminal 27 issoldered to the electrode on the upper face of the piezoelectric element16. The position of this soldering preferably corresponds to a node ofvibration produced in the piezoelectric element 16. This reduces leakageof vibration from the piezoelectric element 16 to the internalconnection terminal 27, allowing for improved driving efficiency. In oneparticularly preferred arrangement, for a concentric area correspondingto each node of vibration of the piezoelectric element 16, the internalconnection terminal 27 extends all the way to its distal end portion ina direction tangential to the concentric area, and the distal endportion of the internal connection terminal 27 is connected to thepiezoelectric element 16 at the point of tangency on the concentricarea. This configuration further reduces leakage of vibration to theinternal connection terminal 27, allowing for a further improvement indriving efficiency while preventing the internal connection terminal 27from breaking owing to vibration.

The spacer plate 19, which is stacked between the power feeding plate 18and the lid plate 20, is stuck on the upper face of the power feedingplate 18 and the lower face of the lid plate 20 by using adhesive (notillustrated) or other materials. The spacer plate 19, which is made ofresin, has a substantially rectangular frame-like shape with an opening49 in plan view. The opening 49 constitutes a part of the pump chamber51 (see FIG. 4). The spacer plate 19 is provided to prevent the solderedportion of the internal connection terminal 27 from coming into contactwith the lid plate 20 when vibration occurs. If the upper face of thepiezoelectric element 16 comes too close to the lid plate 20, theamplitude of vibration decreases owing to air resistance. Accordingly,the spacer plate 19 preferably has a thickness substantially equal to orgreater than the thickness of the piezoelectric element 16.

The lid plate 20 is stacked over the spacer plate 19 such that the lidplate 20 is exposed at the upper principal face 5 of the housing 2. Thelid plate 20 is stuck on the upper face of the spacer plate 19 by usingadhesive (not illustrated) or other materials. The lid plate 20 closesthe top side of the pump chamber 51 (see FIG. 4), and is positionedfacing the vibrating plate 15 with a spacing therebetween. The lid plate20 has the channel hole 50 at the upper principal face 5 of the housing2. The channel hole 50 has a circular shape in plan view. The channelhole 50 communicates with the external space, and also communicates withthe opening 49 of the spacer plate 19, that is, the pump chamber 51. Inthe first embodiment, the channel hole 50 is an outlet for discharginggas to the external space. Although the channel hole 50 is located at aposition away from the center of the lid plate 20 in this example, thechannel hole 50 may be provided near the center of the lid plate 20.

FIG. 3A is a plan view of the vibrating plate 15 and the piezoelectricelement 16 as seen from the top side. FIG. 3B is a plan view of thevibrating plate 15 as seen from the bottom side. FIG. 3C is a side viewof the cross-section of the vibrating plate 15 and the piezoelectricelement 16 taken along C-C′ in FIG. 3A.

As described above, the vibrating plate 15 includes, in plan view, thecentral part 21, the frame part 22, and the connecting parts 23, 24, 25,and 26, and has the openings 43, 44, 45, and 46. The piezoelectricelement 16 is in the form of a disc slightly smaller in diameter thanthe central part 21 of the vibrating plate 15 in plan view. Thepiezoelectric element 16 is stuck on the upper face of the central part21.

The connecting parts 23, 24, 25, and 26 extend radially from the centralpart 21 along the diagonals of the frame part 22 having a rectangularframe-like shape. The connecting parts 23, 24, 25, and 26 respectivelyinclude striking parts 53, 54, 55, and 56. The striking parts 53, 54,55, and 56 are respectively areas in the connecting parts 23, 24, 25,and 26 that are locally increased in width near the boundary adjacent tothe central part 21. Each of the striking parts 53, 54, 55, and 56 has acircular shape that is smaller in diameter than the central part 21 inplan view. The thickness of the vibrating plate 15 is reduced in areasexcluding the striking parts 53, 54, 55, and 56 and the frame part 22 byetching performed from the lower face of the vibrating plate 15, and thestriking parts 53, 54, 55, and 56 and the frame part 22 are thicker thanother areas. That is, the striking parts 53, 54, 55, and 56 and theframe part 22 are formed as projections that project further toward thebottom side than do other areas of the vibrating plate 15.

FIG. 4 is a side view of the cross-section of the pump 1 taken alongX-X′ in FIG. 3B.

The pump 1 includes a housing 52 and the fluid control part 59, with thepump chamber 51 provided inside the housing 52. The housing 52 includesthe cover plate 11, the channel plate 12, a restraining part 58 of theopposed plate 13 that will be described later, the adhesion layer 14,the frame part 22 of the vibrating plate 15, the insulating plate 17,the power feeding plate 18, the spacer plate 19, and the lid plate 20.The fluid control part 59 includes the piezoelectric element 16, thecentral part 21 and the connecting parts 23, 24, 25, and 26 of thevibrating plate 15, and a movable part 57 of the opposed plate 13 thatwill be described later. The fluid control part 59, which is providedinside the pump chamber 51 and vibrates to control fluid, corresponds tothe “fluid control device” according to the present disclosure.

The opposed plate 13 has the channel holes 39 and 40 that are open tothe pump chamber 51, at positions respectively facing substantially thecenter of the striking parts 53 and 54 of the connecting parts 23 and24. Although not illustrated in the cross-sectional view of FIG. 4, theopposed plate 13 has the channel holes 41 and 42 (see FIG. 2) that areopen to the pump chamber 51, at positions respectively facingsubstantially the center of the striking parts 55 and 56 (see FIG. 3) ofthe connecting parts 25 and 26. The striking parts 53, 54, 55, and 56have a diameter larger than the diameter of the channel holes 39, 40,41, and 42.

The areas near the channel holes 39 and 40 of the lower face of theopposed plate 13 are respectively exposed at the openings 35 and 36 ofthe channel plate 12. Although not illustrated in the cross-sectionalview of FIG. 4, the areas near the channel holes 41 and 42 (see FIG. 2)of the lower face of the opposed plate 13 are also respectively exposedat the openings 37 and 38 (see FIG. 2) of the channel plate 12. Thelower face of the opposed plate 13 is secured to the channel plate 12except in areas near the channel holes 39, 40, 41, and 42. Thisconfiguration allows the areas of the opposed plate 13 near the channelholes 39, 40, 41, and 42 to serve as the movable part 57 that is capableof flexion without being restrained by the channel plate 12. Thisconfiguration also allows the portion of the lower face of the opposedplate 13 secured to the channel plate 12 to serve as the restrainingpart 58 that is incapable of flexion and restrains the areas around themovable part 57. The diameter of the movable part 57 and the diameter ofthe striking parts 53, 54, 55, and 56 are desirably relatively similar,but may not necessarily be the same. The opposed plate 13 and thechannel plate 12 may be formed as a single plate member. In that case,the movable part 57 and the restraining part 58 may be formed byproviding the plate member with a thin-walled portion of reducedthickness located near the channel holes 39, 40, 41, and 42, and athick-walled portion of increased thickness surrounding the thinportion.

In the pump 1, application of an alternating-current driving signal tothe external connection terminals 3 and 4 causes an alternating electricfield to be applied in the thickness direction of the piezoelectricelement 16. Then, as the piezoelectric element 16 attempts to expand andcontract isotropically in the in-plane direction, flexural vibrationsare generated concentrically in the thickness direction in the stack ofthe piezoelectric element 16 and the vibrating plate 15. Accordingly, inthe first embodiment, the alternating-current driving signal applied tothe external connection terminals 3 and 4 is set to a predeterminedfrequency so that flexural vibration is produced in the stack of thepiezoelectric element 16 and the vibrating plate 15 in a higher-orderresonant mode.

FIG. 5A schematically illustrates flexural vibration in a higher-orderresonant mode generated in the stack of the piezoelectric element 16 andthe vibrating plate 15. The following description will be directed to athird-order resonant mode.

In the pump 1, the stack of the piezoelectric element 16 and thevibrating plate 15 has a higher-order (and odd-order) resonant mode suchthat the frame part 22 becomes a node, the center of the central part 21becomes a first antinode, and the center of each of the striking parts53, 54, 55, and 56 becomes a second antinode. The frequency of thealternating-current driving signal is set so as to produce such ahigher-order resonant mode. For example, in the third-order resonantmode, the first antinode and the second antinode differ in theirvibration phase by 180 degrees. That is, when the piezoelectric element16 expands, the center of the central part 21 of the vibrating plate 15bends to become convex toward the piezoelectric element 16, and thestriking parts 53, 54, 55, and 56 are displaced in the directionopposite to the piezoelectric element 16. When the piezoelectric element16 contracts, the center of the central part 21 of the vibrating plate15 bends to become concave toward the piezoelectric element 16, and thestriking parts 53, 54, 55, and 56 are displaced toward the piezoelectricelement 16.

FIG. 5B schematically illustrates how the areas near the striking part53 and the movable part 57 vibrate.

When vibration occurs in a higher-order resonant mode, this causes thestriking part 53 of the vibrating plate 15 to vibrate in such a way thatthe striking part 53 is repeatedly displaced upward and downward. Theareas near the striking parts 54, 55, and 56 (see FIG. 3) are alsosubjected to vibration similar to that generated in the area near thestriking part 53. The vibrations produced near the striking parts 53,54, 55, and 56 are in synchronous phase with one another. Then, thestriking parts 53, 54, 55, and 56 are repeatedly struck against a thinfluid layer that is present in the gap between the opposed plate 13 andthe striking parts 53, 54, 55, and 56 inside the pump chamber 51. Thiscauses repeated pressure fluctuations to occur in the fluid positionedfacing the striking parts 53, 54, 55, and 56. The repeated pressurefluctuations are transmitted through the fluid to the movable part 57positioned facing the striking parts 53, 54, 55, and 56. The movablepart 57, which has its dimensions such as diameter and thicknessdesigned to have a predetermined natural frequency, undergoes flexuralvibration in response to the vibration of the striking parts 53, 54, 55,and 56.

As the vibration of the striking parts 53, 54, 55, and 56 and thevibration of the movable part 57 produced in this way become coupled, inthe gap between the opposed plate 13 and the vibrating plate 15 insidethe pump chamber 51, the fluid flows toward the outer periphery of themovable part 57 from the vicinity of the channel holes 39, 40, 41, and42 located at the center of the movable part 57. This creates a negativepressure in the vicinity of the channel holes 39, 40, 41, and 42 insidethe pump chamber 51, causing the fluid to be sucked into the pumpchamber 51 from each of the channel holes 39, 40, 41, and 42. Inside thepump chamber 51, a positive pressure is created in the space locatednear the lid plate 20, and this positive pressure is released at thechannel hole 50 provided in the lid plate 20. Consequently, the fluidsucked into the pump chamber 51 through each of the channel holes 39,40, 41, and 42 exits the pump chamber 51 through the channel hole 50provided in the lid plate 20.

In the pump 1 according to the first embodiment, the fluid is suckedinto the pump chamber 51 through each of the four channel holes 39, 40,41, and 42 in a parallel fashion. This allows for an increase in thetotal amount of fluid entering the pump chamber 51, thus enabling animprovement in the driving efficiency of the pump 1.

Further, the striking parts 53, 54, 55, and 56 with an increased widthare provided inside the pump chamber 51, and the striking parts 53, 54,55, and 56 are positioned facing the areas around the channel holes 39,40, 41, and 42, which directly contribute to pump action, at a closedistance. This configuration allows the amplitude of vibration of thestriking parts 53, 54, 55, and 56 to be increased without decreasing thearea of the fluid positioned facing the striking parts 53, 54, 55, and56.

Further, the striking parts 53, 54, 55, and 56 in the form ofprojections are provided inside the pump chamber 51, and the strikingparts 53, 54, 55, and 56 are positioned facing the areas around thechannel holes 39, 40, 41, and 42, which directly contribute to pumpaction, at a close distance. This configuration allows the spacingbetween the vibrating plate 15 and the opposed plate 13 to be increasedat positions that do not directly contribute to pump action. Thesefeatures make it possible to reduce unwanted load on the piezoelectricelement 16 and the vibrating plate 15, thus enabling improvements infeatures such as the pressure or flow rate of the fluid generated bypump action, and driving efficiency. Although the striking parts 53, 54,55, and 56 are provided in the form of projections in the firstembodiment, the striking parts 53, 54, 55, and 56 may be provided asflat areas with the same thickness as the thickness of the surroundingareas. In that case, the movable part 57 of the opposed plate 13positioned facing the striking parts 53, 54, 55, and 56 may be providedso as to project toward the striking parts 53, 54, 55, and 56.

Preferably, the opposed plate 13, the channel plate 12, and the coverplate 11 are each made of a material with a coefficient of linearexpansion higher than the coefficient of linear expansion of thevibrating plate 15, and bonded to the frame part 22 of the vibratingplate 15 by using a thermosetting adhesive. As a result, the opposedplate 13 can be bowed to become convex toward the vibrating plate 15under normal temperature environments, thus imparting tension to themovable part 57. This tension makes the movable part 57 resistant toslacking. This makes it possible to prevent vibration from beinginhibited by deflection or settling of the movable part 57.

Preferably, the lid plate 20, the spacer plate 19, the power feedingplate 18, the insulating plate 17, the vibrating plate 15, the opposedplate 13, the channel plate 12, and the cover plate 11 all havesubstantially equal coefficients of linear expansion. In particular, thelid plate 20, the vibrating plate 15, the opposed plate 13, the channelplate 12, and the cover plate 11 are preferably made of identical kindsof metals with equal or similar coefficients of linear expansion. Thisreduces variations in the tension on the movable part 57 resulting froma difference in coefficient of linear expansion, thus improving thetemperature characteristics of the pump 1.

Now, a more detailed description will be given of how the movable part57 and the striking parts 53, 54, 55, and 56 vibrate. The movable part57 is designed to have a natural frequency corresponding to a frequencyslightly lower than the driving frequency of the striking parts 53, 54,55, and 56. As a result, the vibration produced in the movable part 57in response to the vibration of the striking parts 53, 54, 55, and 56has substantially the same frequency as the driving frequency of thestriking parts 53, 54, 55, and 56, with a slight phase delay.

Further, the striking parts 53, 54, 55, and 56 have a small diameter incomparison to the distance from the center of the vibrating plate 15 tothe center of the striking parts 53, 54, 55, and 56, that is, thedistance from the first antinode to the second antinode. Thus, thestriking parts 53, 54, 55, and 56 vibrate so as to undergo upward anddownward displacement while keeping a relatively flat shape. Bycontrast, the movable part 57 is restrained at its outer periphery bythe restraining part 58, and has a diameter substantially equal to thediameter of the striking parts 53, 54, 55, and 56. Thus, the movablepart 57 vibrates so as to undergo large upward and downward flexionwithin the area where the movable part 57 is positioned facing each ofthe striking parts 53, 54, 55, and 56.

In this way, a standing-wave vibration that causes upward and downwarddisplacement is produced in each of the striking parts 53, 54, 55, and56, and a standing-wave vibration that causes upward and downwardflexion is produced in the movable part 57. These standing-wavevibrations differ in their wave length and phase. Consequently, thespacing between the striking parts 53, 54, 55, and 56 and the movablepart 57 represented as the difference between these standing-wavevibrations changes with time like a travelling wave travelling from thevicinity of the channel holes 39, 40, 41, and 42 toward the outerperiphery of the movable part 57, because the two standing-wavevibrations differ in their wave length and phase. As a result, in thegap between the striking parts 53, 54, 55, and 56 and the movable part57, the fluid is transferred so as to be squeezed out from the vicinityof the channel holes 39, 40, 41, and 42 toward the outer periphery ofthe movable part 57. This allows the direction of fluid flow to be seteven without the presence of a component such as a check valve in thepump 1, thus facilitating fluid flow. In this respect as well, unwantedload on the piezoelectric element 16 and the vibrating plate 15 can bereduced to enable improvements in features such as the pressure or flowrate of fluid created by pump action, and driving efficiency.

As discussed above, the pump 1 according to the first embodiment allowsdriving efficiency to be improved without an increase in its physicalsize. Alternatively, the pump 1 allows its physical size to be reducedwithout a decrease in driving efficiency.

Second Embodiment

Next, a pump 1A according to a second embodiment of the presentdisclosure will be described with reference to an air pump that sucksgas as an example.

FIG. 6 is an exploded perspective view of the pump 1A. The pump 1Aincludes the following components stacked in the order stated below: acover plate 11A, a channel plate 12A, an opposed plate 13A, the adhesionlayer 14 (not illustrated), the vibrating plate 15, the piezoelectricelement 16, a metal plate 17A, the insulating plate 17, the powerfeeding plate 18, the spacer plate 19, and the lid plate 20. Theadhesion layer 14 (not illustrated), the vibrating plate 15, thepiezoelectric element 16, the insulating plate 17, the power feedingplate 18, the spacer plate 19, and the lid plate 20 are of substantiallythe same configuration as those in the first embodiment. The side wallsurface of each of the vibrating plate 15, the insulating plate 17, thepower feeding plate 18, and the spacer plate 19 that faces the pumpchamber described later can be made to have any suitable shape. In thisexample, the side wall surface has such a shape that the side wallsurface extends along the side wall of each of the central part 21 andthe connecting parts 23, 24, 25, and 26 of the vibrating plate 15 with apredetermined spacing therebetween.

In the second embodiment, the metal plate 17A is stacked between thevibrating plate 15 and the insulating plate 17. The metal plate 17A ismade of a hard metallic material with a density and a Young's modulusgreater than those of the insulating plate 17. Providing the metal plate17A having such characteristics allows the vibrating plate 15 to besecured in place with increased reliability in comparison to when theinsulating plate 17 is directly joined to the vibrating plate 15. Inother words, providing the metal plate 17A makes it possible to reduceleakage of the vibration of the vibrating plate 15 to other components,in comparison to when the insulating plate 17 is directly joined to thevibrating plate 15. This allows the amplitude of vibration of thevibrating plate 15 to be increased, thus enabling an improvement in thedriving efficiency of the pump 1A.

In the second embodiment, the cover plate 11A has channel holes 31A,32A, 33A, and 34A. The channel plate 12A has channels 35A, 36A, 37A, and38A. The opposed plate 13A has openings 39A, 40A, 41A, and 42A inaddition to the channel holes 39, 40, 41, and 42.

FIG. 7A is a plan view of the vibrating plate 15. FIG. 7B is a plan viewof the opposed plate 13A. FIG. 7C is a plan view of the channel plate12A. FIG. 7D is a plan view of the cover plate 11A.

The openings 39A, 40A, 41A, and 42A of the opposed plate 13A illustratedin FIG. 7B are provided to prevent the adhesive of the adhesion layer 14(not illustrated) from flowing out toward the connecting parts 23, 24,25, and 26 from the frame part 22 of the vibrating plate 15 illustratedin FIG. 7A. Accordingly, the openings 39A, 40A, 41A, and 42A arerespectively provided so as to extend along the joints between the framepart 22 and the connecting parts 23, 24, 25, and 26. In other words, theopenings 39A, 40A, 41A, and 42A are provided so as to extend along theouter periphery of the movable part 57. Providing the openings 39A, 40A,41A, and 42A in this way makes it possible to prevent the adhesive ofthe adhesion layer 14 (not illustrated) from flowing out toward andbecoming firmly fixed on the connecting parts 23, 24, 25, and 26. Thisprevents problems such as the adhesive of the adhesion layer 14 (notillustrated) becoming firmly fixed on the connecting parts 23, 24, 25,and 26 and inhibiting vibration of the connecting parts 23, 24, 25, and26. As a result, the vibrating plate 15 is vibrated in a more stablemanner, thus preventing variations in the performance of the pump 1A.Not only the opposed plate 13A but also the channel plate 12A may beprovided with openings having the same shape as that of the openings39A, 40A, 41A, and 42A and used for preventing outflow of adhesive.Outflow of adhesive toward the connecting parts 23, 24, 25, and 26 canbe also reduced by forming the vibrating plate 15 thinner in areas otherthan the striking parts 53, 54, 55, and 56 and the frame part 22 throughetching performed from the lower face of the vibrating plate 15, andforming the vibrating plate 15 thicker in the striking parts 53, 54, 55,and 56 and the frame part 22 than in other areas.

The channels 35A, 36A, 37A, and 38A of the channel plate 12Arespectively have openings 35B, 36B, 37B, and 38B and extensions 35C,36C, 37C, and 38C.

The openings 35B, 36B, 37B, and 38B, each of which has an ellipticalshape in plan view, are respectively positioned facing the channel holes39, 40, 41, and 42 of the opposed plate 13A and their surrounding areas.In plan view, the extensions 35C, 36C, 37C, and 38C are extended fromthe openings 35B, 36B, 37B, and 38B in the circumferential direction ofthe central part 21 of the vibrating plate 15. The extensions 35C, 36C,37C, and 38C respectively communicate with the channel holes 31A, 32A,33A, and 34A of the cover plate 11A described later, in the vicinity oftheir end portions distal from the openings 35B, 36B, 37B, and 38B.Thus, the cover plate 11A and the channel plate 12A each correspond tothe channel part defined in the claims. Providing the extensions 35C,36C, 37C, and 38C in the channel plate 12A in this way allows thechannel holes 39, 40, 41, and 42 of the opposed plate 13A and thechannel holes 31A, 32A, 33A, and 34A of the cover plate 11A to berespectively located at positions away from each other in plan view.This reduces leakage of the vibrating sound generated by vibration ofthe vibrating plate 15 from the channel holes 31A, 32A, 33A, and 34A ofthe cover plate 11A through areas such as the channel holes 39, 40, 41,and 42 of the opposed plate 13A and the channels 35A, 36A, 37A, and 38Aof the channel plate 12A. This enables low-noise construction of thepump 1A.

With respect to the direction of the radius extending toward the outerside portion from the central part 21 of the vibrating plate 15, theopenings 35B, 36B, 37B, and 38B are substantially the same or slightlylarger in dimension than the striking parts 53, 54, 55, and 56 of thevibrating plate 15. Further, with respect to the circumferentialdirection around the central part 21, the openings 35B, 36B, 37B, and38B are respectively sufficiently larger in dimension than the strikingparts 53, 54, 55, and 56 of the vibrating plate 15. That is, theopenings 35B, 36B, 37B, and 38B each have a minor axis extending in theradial direction of the central part 21, and a major axis extending inthe circumferential direction of the central part 21. Since the areas inthe opposed plate 13A positioned facing the openings 35B, 36B, 37B, and38B serve as the movable part 57, the movable part 57 of the opposedplate 13A also has an elliptical shape with a minor axis extending inthe radial direction of the central part 21 and a major axis extendingin the circumferential direction of the central part 21.

FIG. 8 is a side cross-sectional drawing as viewed in the direction ofthe minor axis of the movable part 57, schematically illustrating howthe movable part 57 and the striking part 53 vibrate. The striking parts54, 55, and 56 of the vibrating plate 15 and the movable part 57positioned facing the striking parts 54, 55, and 56 also exhibit asimilar manner of vibration.

FIG. 8A illustrates the same configuration as that of the firstembodiment, that is, a configuration in which the movable part 57 hassubstantially the same diameter as the diameter of the striking part 53.FIG. 8B illustrates the same configuration as that of the secondembodiment, that is, a configuration in which the movable part 57 has adiameter sufficiently larger than the diameter of the striking part 53with respect to the major axis direction.

As described above with reference to the first embodiment, the antinodesof flexural vibration are produced concentrically in plan view in thecentral part 21 of the vibrating plate 15. Thus, in the striking part53, antinodes are produced uniformly in the circumferential direction ofthe central part 21 (the major axis direction of the movable part 57).

Consequently, the striking part 53 moves up and down as viewed incross-section taken in the radial direction of the central part 21 (theminor axis direction of the movable part 57). As the striking part 53moves up and down in this way, at positions inside the striking part 53near its both principal faces, the striking part 53 undergoes expansionin the radial direction of the central part 21 (the minor axis directionof the movable part 57) in areas near one principal face, andcontraction in the radial direction of the central part 21 (the minoraxis direction of the movable part 57) in areas near the other principalface. Such expansion or contraction occurring locally within thestriking part 53 produces an opposite contraction or expansion in adirection orthogonal to this expansion or contraction. That is,expansion occurring locally within the striking part 53 in apredetermined direction (the minor axis direction of the movable part57) creates contraction in a direction (the major axis direction of themovable part 57) orthogonal to the direction of the expansion. Further,contraction occurring locally within the striking part 53 in apredetermined direction (the minor axis direction of the movable part57) creates expansion in a direction (the major axis direction of themovable part 57) orthogonal to the direction of the contraction. Thiscauses the striking part 53 to undergo flexural vibration as viewed inthe minor axis direction of the movable part 57.

This vibration has maximum amplitude in the vicinity of each end of thestriking part 53, as viewed in the cross-section of the striking part 53taken in the radial direction of the central part 21 (the minor axisdirection of the movable part 57). Thus, if the amplitude of vibrationin the vicinity of each end of the striking part 53 is increasedexcessively such as by increasing the driving voltage applied, asillustrated in FIG. 8A, there is a risk that the movable part 57positioned facing the striking part 53, and each end portion of thestriking part 53 may approach and collide with each other.

Accordingly, in the second embodiment, the movable part 57 of theopposed plate 13A is formed in an oval shape, thus allowing the movablepart 57 to be increased in dimension in the major axis direction whileminimizing a decrease in the natural frequency of the movable part 57.This allows the amplitude of vibration of the movable part 57 to beincreased at a position facing each end portion in the major axisdirection of the striking part 53 as illustrated in FIG. 8B. This makesit possible to reduce the risk of collision of the movable part 57 witheach end portion of the striking part 53 positioned facing the movablepart 57. Therefore, the pump 1A makes it possible to prevent problemssuch as generation of abnormal vibration or noise and reduction ofpressure resulting from collision between the movable part 57 and thestriking part 53.

As described above, the movable part 57 of the opposed plate 13Adesirably have such a shape that its major axis extends in thecircumferential direction of the central part 21 (the direction in whichantinodes are uniformly produced in the striking parts 53, 53, 55, and56). Suitable examples of the specific planar shape of the movable part57 include an oval in addition to an ellipse.

Third Embodiment

Next, a pump 1B according to a third embodiment of the presentdisclosure will be described with reference to an air pump that sucksgas as an example.

FIG. 9 is an exploded perspective view of the pump 1B. The pump 1Bincludes the cover plate 11, the channel plate 12, the opposed plate 13,the adhesion layer 14 (not illustrated), the vibrating plate 15, thepiezoelectric element 16, the insulating plate 17, the power feedingplate 18, the spacer plate 19, the lid plate 20, and a stacking plate16B.

The stacking plate 16B is further stacked for the stack of the vibratingplate 15 and the piezoelectric element 16. In the third embodiment, thestacking plate 16B is stacked between the vibrating plate 15 and thepiezoelectric element 16. The stacking plate 16B has substantially thesame disc-like outer shape as that of the piezoelectric element 16, andhas dimensions that are the same as or slightly larger than those of thepiezoelectric element 16 in plan view.

As in the first embodiment, the piezoelectric element 16 is made of, forexample, PZT-based ceramic with a coefficient of linear expansion ofsubstantially zero. The vibrating plate 15 is also made of, for example,SUS430 with a coefficient of linear expansion of approximately10.4×10⁻⁶K⁻¹ as in the first embodiment. The vibrating plate 15 and thepiezoelectric element 16 are thus made of different materials, anddiffer in their coefficient of linear expansion.

This means that in the case of a configuration in which the vibratingplate 15 and the piezoelectric element 16 are directly stuck togetherand stacked as in the first embodiment or second embodiment, unwanteddeformation resulting from temperature fluctuations occurs in the stack.Generally speaking, the stack of the vibrating plate 15 and thepiezoelectric element 16 undergoes a deflection such that when subjectedto higher temperatures, the stack becomes more concave in its side nearthe piezoelectric element 16 having the lower coefficient of linearexpansion, and when subjected to lower temperatures, the stack becomesmore convex in its side near the piezoelectric element 16 having thelower coefficient of linear expansion. If such deformation resultingfrom the difference in coefficient of linear expansion occurs in thestack of the vibrating plate 15 and the piezoelectric element 16, thiscauses, for example, the spacing and parallelism between the vibratingplate 15 (the striking parts 53 to 56) and the opposed plate 13 tochange with temperature. Consequently, depending on conditions such asthe setting of the dimensions of various parts or the design of thematerials of various parts, characteristics such as fluid pressuredistribution and fluid pressure fluctuations in the fluid layersandwiched between the vibrating plate 15 and the opposed plate 13become affected by temperature, causing excessive fluctuations in theflow rate of the pump due to temperature.

Accordingly, in the third embodiment, the stack of the vibrating plate15 and the piezoelectric element 16 is further provided with thestacking plate 16B, thus compensating for thermal deformation resultingfrom the difference in coefficient of linear expansion between thevibrating plate 15 and the piezoelectric element 16. As the stackingplate 16B, a stacking plate with a coefficient of linear expansion and athickness that satisfy a predetermined relationship with respect to thecoefficients of linear expansion of the vibrating plate 15 and thepiezoelectric element 16 is disposed at a suitable position.

Specifically, the stacking plate 16B is stacked between thepiezoelectric element 16 and the vibrating plate 15, and the coefficientof linear expansion of the stacking plate 16B is set to a value equal toor higher than the coefficient of linear expansion of each of thepiezoelectric element 16 and the vibrating plate 15, or a value equal toor lower than the coefficient of linear expansion of each of thepiezoelectric element 16 and the vibrating plate 15. When bonding isperformed at high temperatures, compressive stress is applied to thepiezoelectric element 16. Accordingly, it is desirable to set thecoefficient of linear expansion of the stacking plate 16B equal to orhigher than the coefficient of linear expansion of each of thepiezoelectric element 16 and the vibrating plate 15.

With the stacking plate 16B set in this way, the deformation (stress)resulting from the difference in coefficient of linear expansion betweenthe vibrating plate 15 and the stacking plate 16B, and the deformation(stress) resulting from the difference in coefficient of linearexpansion between the piezoelectric element 16 and the stacking plate16B can be cancelled out by each other. As a result, deformationoccurring in the stack of the stacking plate 16B, the piezoelectricelement 16, and the vibrating plate 15 due to the difference incoefficient of linear expansion can be reduced in comparison to when thevibrating plate 15 and the piezoelectric element 16 are directly stucktogether. Therefore, temperature-induced fluctuations in characteristicssuch as the spacing and parallelism between the striking parts 53 to 56provided in the vibrating plate 15 and the opposed plate 13 can bereduced, and temperature-induced fluctuations in the flow rate generatedby vibration of the striking parts 53 to 56 can be also reduced.

The stacking plate 16B may be made of any suitable material whosecoefficient of linear expansion satisfies the above-mentionedrelationship. Examples of the suitable material that may be used includematerials with coefficients of linear expansion higher than that ofSUS430, and materials with coefficients of linear expansion lower thanthat of PZT-based ceramics.

Even if a material with a coefficient of linear expansion lower thanthat of the piezoelectric element 16 is used for the vibrating plate 15,the coefficient of linear expansion of the stacking plate 16B ispreferably set in the manner as mentioned above. That is, it ispreferable to set the coefficient of linear expansion of the stackingplate 16B to a value equal to or higher than the coefficient of linearexpansion of each of the piezoelectric element 16 and the vibratingplate 15, or a value equal to or lower than the coefficient of linearexpansion of each of the piezoelectric element 16 and the vibratingplate 15. In this case as well, the deformation (stress) resulting fromthe difference in coefficient of linear expansion between the vibratingplate 15 and the stacking plate 16B, and the deformation (stress)resulting from the difference in coefficient of linear expansion betweenthe piezoelectric element 16 and the stacking plate 16B can be cancelledout by each other. As already described, this makes it possible toreduce deformation occurring in the stack of the stacking plate 16B, thepiezoelectric element 16, and the vibrating plate 15 resulting from thedifference in coefficient of linear expansion, in comparison to when thevibrating plate 15 and the piezoelectric element 16 are directly stucktogether.

Fourth Embodiment

Next, a pump 1C according to a fourth embodiment of the presentdisclosure will be described.

FIG. 10 is an exploded perspective view of the pump 1C according to thefourth embodiment of the present disclosure.

The pump 1C, which corresponds to a modification of the third embodimentmentioned above, includes a stacking plate 16C. As in the thirdembodiment mentioned above, the stacking plate 16C is further stackedfor the stack of the vibrating plate 15 and the piezoelectric element16. The stacking plate 16C used, which is disposed at a suitableposition, is a stacking plate that has substantially the same disc-likeouter shape as that of the piezoelectric element 16, has dimensions thatare the same as or slightly larger than those of the piezoelectricelement 16 in plan view, and has a coefficient of linear expansion and athickness that satisfy a predetermined relationship with respect to thevibrating plate 15 and the piezoelectric element 16.

In the fourth embodiment, the stacking plate 16C is stacked not betweenthe vibrating plate 15 and the piezoelectric element 16 but over theprincipal face of the vibrating plate 15 located opposite to the sidewhere the piezoelectric element 16 is stacked. Further, the coefficientof linear expansion of the stacking plate 16C is set to a value lowerthan the coefficient of linear expansion of the vibrating plate 15 andsubstantially equal to the coefficient of linear expansion of thepiezoelectric element 16.

As already mentioned, with the stacking plate 16C set in this way, thedeformation (stress) resulting from the difference in coefficient oflinear expansion between the vibrating plate 15 and the stacking plate16C, and the deformation (stress) resulting from the difference incoefficient of linear expansion between the vibrating plate 15 and thepiezoelectric element 16 can be cancelled out by each other. As aresult, deformation occurring in the stack of the stacking plate 16C,the piezoelectric element 16, and the vibrating plate 15 due to thedifference in coefficient of linear expansion can be reduced incomparison to when the vibrating plate 15 and the piezoelectric element16 are directly stuck together. Therefore, temperature-inducedfluctuations in characteristics such as the spacing and parallelismbetween the striking parts 53 to 56 provided in the vibrating plate 15and the opposed plate 13 can be reduced, and temperature-inducedfluctuations in the flow rate generated by vibration of the strikingparts 53 to 56 can be also reduced.

The stacking plate 16C may be made of any suitable material whosecoefficient of linear expansion satisfies the above-mentionedrelationship. Examples of the suitable material that may be used includemetallic materials with coefficients of linear expansion higher thanthat of SUS430, and resin materials.

Now, suppose that a material with a coefficient of linear expansionlower than that of the piezoelectric element 16 is used for thevibrating plate 15. In this case, the coefficient of linear expansion ofthe stacking plate 16C is preferably set in a manner opposite to thatmentioned above. That is, the coefficient of linear expansion of thestacking plate 16C may be set higher than the coefficient of linearexpansion of the vibrating plate 15. In this case as well, thedeformation (stress) resulting from the difference in coefficient oflinear expansion between the vibrating plate 15 and the stacking plate16C, and the deformation (stress) resulting from the difference incoefficient of linear expansion between the vibrating plate 15 and thepiezoelectric element 16 can be cancelled out by each other. As alreadymentioned, this makes it possible to reduce deformation occurring in thestack of the stacking plate 16C, the piezoelectric element 16, and thevibrating plate 15 due to the difference in coefficient of linearexpansion, in comparison to when the vibrating plate 15 and thepiezoelectric element 16 are directly stuck together.

Fifth Embodiment

Next, the pump 1D according to a fifth embodiment of the presentdisclosure will be described.

FIG. 11 is an exploded perspective view of the pump 1D according to thefifth embodiment of the present disclosure.

The pump 1D, which corresponds to a modification of the third and fourthembodiments mentioned above, includes a stacking plate 16D. As in thethird and fourth embodiments mentioned above, the stacking plate 16D isfurther stacked for the stack of the vibrating plate 15 and thepiezoelectric element 16. The stacking plate 16D used, which is disposedat a suitable position, has substantially the same disc-like outer shapeas that of the piezoelectric element 16, has dimensions that are thesame as or slightly larger than those of the piezoelectric element 16 inplan view, and has a coefficient of linear expansion and a thicknessthat satisfy a predetermined relationship with respect to the vibratingplate 15 and the piezoelectric element 16.

In the fifth embodiment, the stacking plate 16D is stacked neitherbetween the vibrating plate 15 and the piezoelectric element 16 nor overthe principal face of the vibrating plate 15 located opposite to theside where the piezoelectric element 16 is stacked. Instead, thestacking plate 16D is stacked over the principal face of thepiezoelectric element 16 opposite to the side where the vibrating plate15 is stacked. Further, the coefficient of linear expansion of thestacking plate 16D is set to a value higher than the coefficient oflinear expansion of the piezoelectric element 16 and substantially equalto the coefficient of linear expansion of the vibrating plate 15. Thethickness of the stacking plate 16D is set such that the larger thedifference in coefficient of linear expansion between the piezoelectricelement 16 and the vibrating plate 15, the larger the thickness, andconversely, the smaller the difference in coefficient of linearexpansion between the piezoelectric element 16 and the vibrating plate15, the smaller the thickness.

As already mentioned, with the stacking plate 16D set in this way, thedeformation (stress) resulting from the difference in coefficient oflinear expansion between the vibrating plate 15 and the piezoelectricelement 16, and the deformation (stress) resulting from the differencein coefficient of linear expansion between the piezoelectric element 16and the stacking plate 16D can be cancelled out by each other. As aresult, deformation occurring in the stack of the stacking plate 16D,the piezoelectric element 16, and the vibrating plate 15 due to thedifference in coefficient of linear expansion can be reduced incomparison to when the vibrating plate 15 and the piezoelectric element16 are directly stuck together. Therefore, temperature-inducedfluctuations in characteristics such as the spacing and parallelismbetween the striking parts 53 to 56 provided in the vibrating plate 15and the opposed plate 13 can be reduced, and temperature-inducedfluctuations in the flow rate generated by vibration of the strikingparts 53 to 56 can be also reduced.

The stacking plate 16D may be made of any suitable material whosecoefficient of linear expansion satisfies the above-mentionedrelationship. Examples of the suitable material that may be used includemetallic materials with coefficients of linear expansion higher thanthat of PZT-based ceramics, and resin materials.

Now, suppose that a material with a coefficient of linear expansionlower than that of the piezoelectric element 16 is used for thevibrating plate 15. In this case, the coefficient of linear expansion ofthe stacking plate 16D is preferably set in a manner opposite to thatmentioned above. That is, the coefficient of linear expansion of thestacking plate 16D may be set lower than the coefficient of linearexpansion of the piezoelectric element 16. In this case as well, thedeformation (stress) resulting from the difference in coefficient oflinear expansion between the vibrating plate 15 and the piezoelectricelement 16, and the deformation (stress) resulting from the differencein coefficient of linear expansion between the stacking plate 16D andthe piezoelectric element 16 can be cancelled out by each other. Asalready mentioned, this makes it possible to reduce deformationoccurring in the stack of the stacking plate 16D, the piezoelectricelement 16, and the vibrating plate 15 due to the difference incoefficient of linear expansion, in comparison to when the vibratingplate 15 and the piezoelectric element 16 are directly stuck together.With this configuration, although the stacking plate 16D hindersmovement of the piezoelectric element 16, the piezoelectric element 16is able to move as the piezoelectric element 16 is located away to oneside from the neutral plane of the three layers made up of the stackingplate 16D, the piezoelectric element 16, and the vibrating plate 15.

Other Embodiments

Next, other embodiments of the present disclosure will be described.

FIG. 12A is a perspective view of an opposed plate 61 constituting apump according to a sixth embodiment of the present disclosure. Theopposed plate 61 includes channel-hole gathering parts 62, 63, 64, and65 at positions corresponding to the respective striking parts 53, 54,55, and 56 of the vibrating plate 15. Each of the channel-hole gatheringparts 62, 63, 64, and 65 is made up of a plurality of channel holes thatare integrated together. Each of the pump and the fluid control partaccording to the present disclosure may include the opposed plate 61configured as mentioned above.

FIG. 12B is a cross-sectional view of a pump 71 according to a seventhembodiment of the present disclosure. In the pump 71, a striking part 72in the form of a projection is provided also in the central part 21 ofthe vibrating plate 15. Further, a channel hole 73 of the opposed plate13, an opening 74 of the channel plate 12, and a channel hole 75 of thecover plate 11 are provided at a position facing the striking part 72.In the pump and the fluid control part according to the presentdisclosure, components such as a channel hole for sucking fluid from theoutside, and a striking part may be provided in this way also in thearea located facing the central plate. As a result, the number ofchannel holes for sucking fluid from the outside can be increased, thusenabling a further increase in flow rate as well as a furtherimprovement in driving efficiency.

FIG. 12C is a cross-sectional view of a pump 81 according to an eighthembodiment of the present disclosure. The pump 81 includes, in additionto the piezoelectric element 16 stuck on the upper face of the vibratingplate 15, a piezoelectric element 16′ stuck on the lower face of thevibrating plate 15. That is, in the pump 81, the piezoelectric element16, the vibrating plate 15, and the piezoelectric element 16′ are formedas a bimorph structure. When a stack of piezoelectric element andvibrating plate is formed as a bimorph structure in this way, theamplitude of vibration of the resulting stack of piezoelectric elementand vibrating plate can be increased in comparison to the structure(unimorph structure) of the stack of piezoelectric element and vibratingplate described above with reference to the first to third embodiments.Although the manner of feeding power for cases where two piezoelectricelements are disposed so as to form a bimorph structure is notparticularly limited, a specific example of how power is fed in suchcases will be described later.

FIG. 13A is a cross-sectional view of a pump 91A according to a ninthembodiment of the present disclosure. In the pump 91A, an opposed plateand channel holes of the opposed plate are disposed on the same side aseach principal face of a vibrating plate. Specifically, the pump 91Aincludes a vibrating plate 15′ whose upper and lower faces are eachprojected to form a striking part 94. Further, the pump 91A has, inaddition to the cover plate 11, the channel plate 12, the opposed plate13, and the adhesion layer 14 located on the same side as the lower faceof the vibrating plate 15′, a cover plate 11′, a channel plate 12′, anopposed plate 13′, and an adhesion layer 14′ disposed on the same sideas the upper face of the vibrating plate 15′. The cover plate 11′, thechannel plate 12′, and the opposed plate 13′ are substantially the samein shape as and arranged in an order opposite to the cover plate 11, thechannel plate 12, and the opposed plate 13, respectively. That is, thecover plate 11′, the channel plate 12′, and the opposed plate 13′include channel holes 39′ and 40′, openings 35′ and 36′, and channelholes 31′ and 32′ that are located facing the upper face of the strikingpart 94. Unlike the cover plate 11, the channel plate 12, and theopposed plate 13, the cover plate 11′, the channel plate 12′, and theopposed plate 13′ respectively have openings 91, 92, and 93 at theircentral parts. The openings 91, 92, and 93 communicate the pump chamberwith the external space. With this configuration, the openings 91, 92,and 93 have a function opposite to the channel holes 31, 32, 31′, and32′, that is, function as an outlet for discharging gas to the outside.

In the pump and the fluid control part according to the presentdisclosure, the channel holes of the opposed plates may be provided bothabove and below the vibrating plate as described above. This allows fora further increase in the number of channel holes of the opposed plates,thus enabling a further increase in flow rate as well as a furtherimprovement in driving efficiency.

FIG. 13B is a cross-sectional view of a pump 91B according to a tenthembodiment of the present disclosure. In the pump 91B, which correspondsto a modification of the pump 91A according to the ninth embodiment, anopposed plate and channel holes of the opposed plate are located on thesame side as each principal face of a vibrating plate. In the pump 91B,an opening 95, which has the function of an outlet opposite to thefunction of the channel holes 31, 32, 31′, and 32′, is located not inthe cover plate 11′, the channel plate 12′, and the opposed plate 13′but at the lateral side of the vibrating plate 15′.

In the pump and the fluid control part according to the presentdisclosure, an opening that has the function of an outlet opposite tothe function of the channel holes 31, 32, 31′, and 32′ may be providednot above or below the vibrating plate but at the lateral side of thevibrating plate. This configuration allows the inlet and the outlet tobe spaced apart from each other. This allows for increased freedom inthe installation of the device increases, thus enabling efficientsuction and discharge of gas.

FIG. 13C is a cross-sectional view of a pump 91C according to aneleventh embodiment of the present disclosure. The pump 91C correspondsto a modification of the pumps 91A and 91B according to the ninth andtenth embodiments. In the pump 91C, the cover plates 11 and 11′ areprovided with no channel holes, and the channel plates 12 and 12′ areprovided with channels 96 that communicate the openings 35 and 36 andthe openings 35′ and 36′ with each other, with openings 97 beingprovided at the lateral sides of the channel plates 12 and 12′ so as tocommunicate with each other via the channels 96.

In the pump and the fluid control part according to the presentdisclosure, both the inlet and the outlet may be made to communicatewith the outside not at positions above and below the vibrating platebut at the lateral sides of the vibrating plate. This configurationallows gas to be sucked in and discharged even when components such asan external board and an external housing are disposed both over andunder the pump. Further, each of the inlet and the outlet areas can begathered in one space. These features also lead to increased freedom inthe installation of the device, thus allowing for efficient suction anddischarge of gas.

Twelfth Embodiment

Next, an example of wiring structure employed when two piezoelectricelements and two vibrating plates are used to achieve a bimorphstructure will be described with reference to a pump 201 according to atwelfth embodiment of the present disclosure.

FIG. 14 is an exploded perspective view of the pump 201. The pump 201includes cover plates 211 and 211′, channel plates 212 and 212′, opposedplates 213 and 213′, insulating layers 214 and 214′, a vibrating plate215, piezoelectric elements 216 and 216′, and power feeding plates 217and 217′. The cover plate 211, the channel plate 212, the opposed plate213, the insulating layer 214, the piezoelectric element 216, and thepower feeding plate 217 are disposed on the same side as the lower faceof the vibrating plate 215. The cover plate 211′, the channel plate212′, the opposed plate 213′, the insulating layer 214′, thepiezoelectric element 216′, and the power feeding plate 217′ aredisposed on the same side as the upper face of the vibrating plate 215.

The cover plate 211 is exposed at the lower principal face of the pump201, and stuck on the lower face of the channel plate 212. The coverplate 211 has a channel hole 231 at the lower principal face of the pump201. The channel hole 231 has a circular shape. In the twelfthembodiment, the channel hole 231 is an inlet for sucking gas from theexternal space.

The channel plate 212 is stacked between the cover plate 211 and theopposed plate 213. The channel plate 212 has openings 232, 233, and 234,and a channel 235 that are provided at its upper and lower faces. Theopening 232, which has a circular shape with substantially the samediameter as that of the channel hole 231 of the cover plate 211,communicates with the channel hole 231 of the cover plate 211. Theopenings 233, which have a circular shape with substantially the samediameter as the diameter of striking parts 224 described later, are eachprovided at a position facing the corresponding striking part 224. Theopening 234, which constitutes a part of the pump chamber, is providedat a position facing the piezoelectric element 216 and the power feedingplate 217. The channel 235, which is sandwiched by the opposed plate 213and the cover plate 211 from above and below, extends so as tocommunicate the openings 232 and 233 with each other.

The opposed plate 213 is stacked between the channel plate 212 and thevibrating plate 215. The opposed plate 213 also has channel holes 236and 237, and an opening 238 provided at its upper and lower faces. Thechannel hole 236, which has a circular shape with substantially the samediameter as that of the opening 232 of the channel plate 212,communicates with the opening 232 of the channel plate 212. The channelholes 237, which are provided at positions facing the striking parts 224described later, have a circular shape that is smaller in diameter thanthe striking parts 224 and the openings 233 of the channel plate 212.The channel holes 237 communicate with the pump chamber and the openings233 of the channel plate 212. The opening 238, which constitutes a partof the pump chamber, is provided at a position facing the piezoelectricelement 216 and the power feeding plate 217.

The vibrating plate 215 is stacked between the opposed plate 213 and theopposed plate 213′. Although not illustrated in FIG. 14, an adhesionlayer containing particles is provided at a predetermined thicknessbetween the vibrating plate 215 and the opposed plate 213, and betweenthe vibrating plate 215 and the opposed plate 213′. The particlesforming the adhesion layer may be either electrically conductive ornon-electrically conductive.

The vibrating plate 215 has a central part 221, a frame part 222, andconnecting parts 223. The connecting parts 223 are provided with thestriking part 224. The vibrating plate 215 has an opening 239 surroundedby the central part 221, the frame part 222, and the connecting parts223, and a channel hole 240 provided in the frame part 222. The opening239 constitutes a part of the pump chamber. The channel hole 240, whichhas a circular shape with substantially the same diameter as that of thechannel hole 236 of the opposed plate 213, communicates with the channelhole 236 of the opposed plate 213.

The vibrating plate 215 includes an upper-face lateral groove 226′provided in the upper face of one side of the frame part 222, and alower-face lateral groove 226 provided in the lower face of one side ofthe frame part 222 so as to overlap the upper-face lateral groove 226′.The upper-face lateral groove 226′ and the lower-face lateral groove 226extend outward from the opening 239.

The opposed plate 213′ is stacked between the channel plate 212′ and thevibrating plate 215. The opposed plate 213 has channel holes 236′ and237′, and an opening 238′ that are provided at its upper and lowerfaces. The channel hole 236′, which has a circular shape withsubstantially the same diameter as that of the channel hole 240 of thevibrating plate 215, communicates with the channel hole 240 of thevibrating plate 215. The channel holes 237′, which are provided atpositions facing the striking parts 224, have a circular shape with adiameter smaller than the diameter of the striking parts 224, andcommunicate with the pump chamber. The opening 238′, which constitutes apart of the pump chamber, is provided at a position facing thepiezoelectric element 216′ and the power feeding plate 217′.

The channel plate 212′ is stacked between the cover plate 211′ and theopposed plate 213′. The channel plate 212′ has openings 232′, 233′, and234′, and a channel 235′ that are provided at its upper and lower faces.The opening 232′, which has a circular shape with substantially the samediameter as that of the channel hole 236′ of the opposed plate 213′,communicates with the channel hole 236′ of the opposed plate 213′. Theopenings 233′, which have a circular shape with substantially the samediameter as the diameter of the striking parts 224, are each provided ata position facing the corresponding striking part 224, and communicatewith the channel holes 237′ of the opposed plate 213′. The opening 234′,which constitutes a part of the pump chamber, is provided at a positionfacing the piezoelectric element 216′ and the power feeding plate 217′.The channel 235′, which is sandwiched by the cover plate 211′ and theopposed plate 213′ from above and below, extends so as to communicatethe openings 232′ and 233′ with each other.

The cover plate 211′ is exposed at the upper principal face of the pump201, and stuck on the upper face of the channel plate 212′. The coverplate 211′ has a channel hole 231′ at the upper principal face of thepump 201. The channel hole 231′ has a circular shape, and communicateswith the opening 234′ (pump chamber) of the channel plate 212′. In thetwelfth embodiment, the channel hole 231′ is an outlet for discharginggas to the external space.

The piezoelectric element 216, which is disc-shaped, is stuck onto thelower face of the central part 221 of the vibrating plate 215. The upperface of the piezoelectric element 216 is electrically connected to thefirst external connection terminal 225 through the vibrating plate 215.

The piezoelectric element 216′, which is disc-shaped, is stuck onto theupper face of the central part 221 of the vibrating plate 215. The lowerface of the piezoelectric element 216′ is electrically connected to thefirst external connection terminal 225 through the vibrating plate 215.

In the present example, the power feeding plate 217 is in the form of abeam that is bent at its distal end. The distal end of the power feedingplate 217 is joined to the lower face of the piezoelectric element 216by a method such as soldering, thus mechanically and electricallyconnecting the distal end to the lower face of the piezoelectric element216. The proximal end of the power feeding plate 217 extends to theoutside through the lower-face lateral groove 226 of the vibrating plate215. In the present example, the power feeding plate 217′ is in the formof a beam that is bent at its distal end in a direction opposite to thepower feeding plate 217. The distal end of the power feeding plate 217′is joined to the upper face of the piezoelectric element 216′ by amethod such as soldering, thus mechanically and electrically connectingthe distal end to the upper face of the piezoelectric element 216′. Theproximal end of the power feeding plate 217′ extends to the outsidethrough the upper-face lateral groove 226′ of the vibrating plate 215.

The insulating layer 214 is made of an adhesive containing insulatingparticles, and secures the power feeding plate 217 inside the lower-facelateral groove 226. The insulating layer 214′ is made of an adhesivecontaining insulating particles, and secures the power feeding plate217′ inside the upper-face lateral groove 226′.

FIG. 15A is a perspective view of a stack made up of the vibrating plate215, the piezoelectric elements 216 and 216′ (the piezoelectric element216 is not illustrated), the power feeding plates 217 and 217′, and theinsulating layers 214 and 214′. FIG. 15B is an enlarged perspective viewof an area in the vicinity of the insulating layers 214 and 214′.

The insides of the upper-face lateral groove 226′ and the lower-facelateral groove 226 of the frame part 222 are respectively filled withthe coatings of the insulating layer 214′ and the insulating layer 214.The power feeding plates 217 and 217′ are respectively positioned so asto pass through the insides of the insulating layers 214 and 214′. As aresult, the power feeding plates 217 and 217′ are led to the outsidewithout being bright into electrical continuity with the vibrating plate215 and the first external connection terminal 225. The proximal end ofeach of the power feeding plates 217 and 217′ thus functions as a secondexternal connection terminal.

The insulating layers 214 and 214′ are each made of an adhesive havinginsulating property. Non-electrically conductive particles are mixed inthe adhesive. This ensures that the insulating layers 214 and 214′ witha thickness equal to or greater than the particle diameter of thenon-electrically conductive particles is present between the powerfeeding plates 217 and 217′ and the vibrating plate 215, respectively.

The insulating layers 214 and 214′ may not contain non-electricallyconductive particles. In that case, it is desirable to, for example,provide an insulating coating of an insulating material or an oxide filmat locations where the power feeding plate 217 or 217′ or the vibratingplate 215 is exposed inside the upper-face lateral groove 226′ or thelower-face lateral groove 226. This configuration also reliably preventselectrical continuity between the power feeding plates 217 and 217′, andthe vibrating plate 215 and the first external connection terminal 225.

In the pump 201 configured as described above, driving the piezoelectricelements 216 and 216′ causes gas to be sucked in from the outsidethrough the channel hole 231 of the cover plate 211 illustrated in FIG.14. Then, the gas flows into the pump chamber from the channel hole 231of the cover plate 211, through the opening 232, the channel 235, andthe openings 233 of the channel plate 212, and the channel holes 237 ofthe opposed plate 213. At the same time, fluid flows into the pumpchamber in a parallel fashion from the channel hole 231 of the coverplate 211, through the opening 232 of the channel plate 212, the channelhole 236 of the opposed plate 213, the channel hole 240 of the vibratingplate, the channel hole 236′ of the opposed plate 213′, the opening232′, the channel 235′, and the openings 233′ of the channel plate 212′,and the channel holes 237′ of the opposed plate 213′. Then, the fluid isdischarged to the outside from the pump chamber through the channel hole231′ of the cover plate 211′.

Therefore, in the pump and the fluid control device according to thetwelfth embodiment as well, the channel holes of the opposed plates canbe positioned both above and below the vibrating plate, thus enabling afurther increase in suction flow rate as well as a further improvementin driving efficiency. Further, the inlet areas through which gas issucked in from the outside and the outlet areas through which gas isdischarged to the outside can be gathered in one space. This increasesthe freedom in the installation of the device, thus allowing forefficient suction and discharge of gas.

Although the present disclosure can be practiced as in the embodimentsdescribed above, the present disclosure can be also practiced in otherembodiments. For example, although the above-described embodiments use,as a driver, a piezoelectric element that undergoes expansion andcontraction in the in-plane direction, the present disclosure is notlimited to this. For example, the vibrating plate may be vibrated in aflexural manner through electromagnetic drive. Although thepiezoelectric element is made of PZT-based ceramic in theabove-described embodiments, the present disclosure is not limited tothis. For example, the piezoelectric element may be made of a non-leadpiezoelectric ceramic material such as potassium sodium niobate-basedceramic and alkali niobate-based ceramic.

In the above-described embodiments, the striking part provided in eachof the connecting parts has such a shape that is locally increased inwidth relative to the surrounding areas of the connecting part andprojects toward the bottom side. However, the present disclosure is notlimited to this. For example, the striking part may be the same in widthor thickness as other areas in the connecting part.

Although the piezoelectric element and the central part of the vibratingplate, and the striking parts and the movable part have diameterssimilar to each other in the above-described embodiments, the presentdisclosure is not limited to this. For example, the central part of thevibrating plate may be sufficiently larger than the piezoelectricelement. Further, either the striking parts or the movable part may besufficiently larger than the other. Although parts such as thepiezoelectric element, the central part of the vibrating plate, and thestriking parts are circular in shape in the above-described embodiments,the present disclosure is not limited to this. For example, parts suchas the piezoelectric element, the central part of the vibrating plate,and the striking parts may be rectangular or polygonal in shape.

Although the vibrating plate is provided with four connecting parts andfour striking parts, and the opposed plate is provided with four channelholes and the movable part in the above-described embodiments, thepresent disclosure is not limited to this. Parts such as thepiezoelectric element, the central part of the vibrating plate, and thestriking parts may be rectangular or polygonal in shape. For example,parts such as the connecting parts, the striking parts, the channelholes of the opposed plate, and the movable part may be provided in two,three, or five or more locations.

Although the frequency of the alternating-current driving signal isdetermined so as to vibrate the vibrating plate in a third-orderresonant mode in the above-described embodiments, the present disclosureis not limited to this. For example, the frequency of thealternating-current driving signal may be determined so as to vibratethe fluid control part in other resonant modes such as a fifth-orderresonant mode and a seventh-order resonant mode.

Although the above-described embodiments use a gas as an example offluid, the present disclosure is not limited to this. For example, thefluid may be a liquid, a gas-liquid mixture, a solid-liquid mixture, ora solid-gas mixture. Although fluid is sucked into the pump chamberthrough the channel holes provided in the opposed plate in theabove-described embodiments, the present disclosure is not limited tothis. For example, fluid may be discharged from the pump chamber throughthe channel holes provided in the opposed plate. Whether fluid is suckedor discharged through the channel holes provided in the opposed plate isdetermined in accordance with the direction of a travelling waverepresented as the difference in vibration between the striking partsand the movable part.

Lastly, the foregoing description of the embodiments is intended to beillustrative in all respects and not to be construed as limiting. Thescope of the present disclosure is defined not by the above embodimentsbut by the appended claims. Further, the scope of the present disclosureis intended to include all modifications that fall within the meaningand scope of the claims and any equivalents thereof.

-   -   1, 1A, 1B, 1C, 1D, 71, 81, 91A, 91B, 91C, 201 pump    -   2 housing    -   3, 4 external connection terminal    -   5, 6 principal face    -   11, 11′, 11A, 211, 211′ cover plate    -   12, 12′, 12A, 212, 212′ channel plate    -   13, 13′, 13A, 61, 213, 213′ opposed plate    -   14, 14′, 214, 214′ adhesion layer    -   15, 15′, 215 vibrating plate    -   16, 16′, 216, 216′ piezoelectric element    -   16B, 16C, 16D, 16D stacking plate    -   17 insulating plate    -   17A metal plate    -   18, 217, 217′ power feeding plate    -   19 spacer plate    -   20 lid plate    -   21, 221 central part    -   22, 222 frame part    -   23, 24, 25, 26, 223 connecting part    -   27 internal connection g terminal    -   31, 32, 33, 34, 31′, 32′, 31A, 32A, 33A, 34A, 39, 39′, 40, 40′,        41, 42, 50, 73, 75, 231, 231′, 236, 237, 236′, 237′, 240 channel        hole    -   35, 36, 35′, 36′, 37, 38, 39′, 40′, 35B, 36B, 37B, 38B, 39A,        40A, 41A, 42A, 43, 44, 45, 46, 47, 48, 49, 74, 91, 92, 93, 94,        97, 232, 233, 234, 232′, 233′, 234′, 238, 238′, 239 opening    -   35A, 36A, 37A, 38A, 96, 235, 235′ channel    -   35C, 36C, 37C, 38C extension    -   51 pump chamber    -   52 housing    -   53, 54, 55, 56, 72, 94, 224 striking part    -   57 movable part    -   58 restraining part    -   59 fluid control part (fluid control device)    -   62, 63, 64, 65 channel-hole gathering part    -   225 external connection terminal    -   226 lower-face lateral groove    -   226′ upper-face lateral groove

1. A fluid control device comprising: a vibrating plate having a centralpart, a frame part surrounding the central part, and a connecting partconnecting between the central part and the frame part; a driver stackedover the central part, the driver being configured to vibrate thevibrating plate in a flexural manner from the central part to theconnecting part; and an opposed plate stacked over the frame part, theopposed plate being spaced apart from and opposed to at least theconnecting part, wherein the vibrating plate has a resonant mode suchthat an antinode occurs in each of the central part and the connectingpart, and wherein the opposed plate has a plurality of channel holesthough which a fluid flows, each of the channel holes being located at aposition opposed to the connecting part.
 2. The fluid control deviceaccording to claim 1, wherein the connecting part includes, at aposition opposed to each of the channel holes, a striking part having awidth is locally increased as viewed from the channel holes.
 3. Thefluid control device according to claim 1, wherein the connecting partincludes, at a position opposed to each of the channel holes, aprojection that projects toward the channel hole.
 4. The fluid controldevice according to claim 1, wherein the opposed plate includes, aroundeach of the channel holes, a projection projecting toward the vibratingplate.
 5. The fluid control device according to claim 1, wherein theopposed plate includes a movable part bendable and provided around eachof the channel holes, and a restraining part restraining an area aroundthe movable part.
 6. The fluid control device according to claim 5,wherein the movable part has such a shape in a plan view having a majoraxis extending in a direction of producing antinodes uniformly in theconnecting part, and a minor axis extending in a direction orthogonal tothe major axis.
 7. The fluid control device according to claim 5,further comprising a channel part stacked over a side of the opposedplate opposite to the vibrating plate, the channel part having a channelcommunicating with each of the channel holes of the opposed plate,wherein the channel of the channel part includes an opening opposed toeach of the channel holes of the opposed plate and an area around eachof the channel holes, an extension extended laterally from the opening,and a channel hole opened to an external space and communicating withthe opening through the extension.
 8. The fluid control device accordingto claim 7, wherein at least one of the channel part and the opposedplate has a coefficient of linear expansion substantially equal to acoefficient of linear expansion of the vibrating plate.
 9. The fluidcontrol device according to claim 1, wherein the opposed plate isstacked over the vibrating plate by using an adhesive, and wherein theopposed plate has an opening extending along a boundary between theframe part and the connecting part of the vibrating plate.
 10. The fluidcontrol device according to claim 1, wherein the vibrating plate and theopposed plate are each made of an electrically conductive material,wherein the opposed plate and the vibrating plate are stacked by usingan adhesive containing electrically conductive particles, and whereineach of the electrically conductive particles has a particle diameterequivalent to a spacing between the opposed plate and the vibratingplate.
 11. The fluid control device according to claim 1, furthercomprising: an insulating layer stacked over the frame part, theinsulating layer being positioned over a side of the vibrating plateover which the driver is stacked; and a power feeding plate stacked overthe vibrating plate with the insulating layer interposed between thepower feeding plate and the vibrating plate, the power feeding platehaving an internal connection terminal formed in a part of the powerfeeding plate, the internal connection terminal being connected to thedriver.
 12. The fluid control device according to claim 11, wherein theinsulating layer includes an insulating coating located between thevibrating plate and the power feeding plate.
 13. The fluid controldevice according to claim 11, wherein the insulating layer includes anadhesive mixed with non-electrically conductive particles.
 14. The fluidcontrol device according to claim 11, further comprising a metal platestacked over the frame part of the vibrating plate.
 15. The fluidcontrol device according to claim 11, wherein the frame part of thevibrating plate has a groove located on a side of the vibrating plateover which the driver is stacked, and wherein the insulating layer andthe power feeding plate are disposed in the groove.
 16. The fluidcontrol device according to claim 1, wherein the opposed plate hasanother channel hole also at a position opposed to the central part. 17.The fluid control device according to claim 1, further comprising astacking plate further stacked over the vibrating plate and the driver,wherein the vibrating plate, the driver, and the stacking plate comprisethree layers including an upper layer, a middle layer, and a lowerlayer, and wherein a magnitude relationship of a coefficient of linearexpansion of the middle layer with respect to a coefficient of linearexpansion of the upper layer is identical to a magnitude relationship ofa coefficient of linear expansion of the middle layer with respect to acoefficient of linear expansion of the lower layer.
 18. The fluidcontrol device according to claim 17, wherein among the three layersincluded in the vibrating plate, the driver, and the stacking plate, acomponent corresponding to a layer in contact with the driver has acoefficient of linear expansion greater than a coefficient of linearexpansion of the driver.
 19. The fluid control device according to claim1, wherein the opposed plate includes a first opposed plate and a secondopposed plate, the first opposed plate being opposed to one principalface of the vibrating plate, the second opposed plate being opposed toanother principal face of the vibrating plate.
 20. The fluid controldevice according to claim 1, wherein the driver includes a first driverand a second driver, the first driver being opposed to one principalface of the vibrating plate, the second driver being opposed to anotherprincipal face of the vibrating plate.
 21. A pump comprising the fluidcontrol device according to claim 1, wherein the pump further comprisesa pump chamber accommodating the vibrating plate and the driver, andwherein the opposed plate forms a part of an inner wall of the pumpchamber.